1. Field of the Invention
The present invention relates to an image-forming method used in, for example, electrophotographic apparatuses, electrostatic recording apparatuses, and electrostatic printing apparatuses.
2. Description of the Related Art
Full-color image-forming apparatuses such as full-color printers and full-color copiers have in recent years been required to accommodate a variety of transfer materials, including not only ordinary paper but also recycled paper, which exhibits a large surface unevenness. In order to respond to these demands, transfer methods that use an intermediate transfer member have become the most prominent of the transfer methods used in full-color image-forming apparatuses.
Transfer methods that use an intermediate transfer member require a primary transfer step in which the toner image is transferred from the surface of the photosensitive member (electrophotographic photosensitive member) to the surface of the intermediate transfer member, and a secondary transfer step in which the toner image transferred to the surface of the intermediate transfer member is transferred to the transfer material. Since the number of transfers in transfer methods that use an intermediate transfer member is larger than in transfer methods that do not use an intermediate transfer member, reductions in the dot reproducibility (coarseness) and reductions in the transfer efficiency are a concern with the former.
In addition, many image-forming apparatuses are equipped with a mechanism that uses a cleaning member, e.g., a cleaning blade, to wipe off the toner (untransferred toner) that remains on the surface of the photosensitive member and the surface of the intermediate transfer member. However, residual toner is prone to slip through when high-speed image output is carried out, and over the long-term residual toner can end up accumulating on the surface of the photosensitive member and the surface of the intermediate transfer material. This has resulted in contamination of the photosensitive member and intermediate transfer member by the toner.
One method introduced to improve the primary transferability and improve the anti-contamination behavior of the photosensitive member has been to make the attachment force of the intermediate transfer member surface for the toner smaller than the attachment force of the photosensitive member surface for the toner and thereby facilitate migration of the toner from the photosensitive member to the intermediate transfer member.
An image-forming method is disclosed in Japanese Patent Application Laid-open No. 2003-202785 in which the contact angle relative to water of the surface of the intermediate transfer member is made smaller than the contact angle relative to water of the surface of the photosensitive member.
An image-forming method is disclosed in Japanese Patent Application Laid-open No. 2006-84840 which uses a photosensitive member having a contact angle relative to water at its surface of at least 95° and a ten-point mean roughness Rz for its surface of not more than 2 μm and an intermediate transfer member having a contact angle relative to water at its surface of at least 95° and a ten-point mean roughness Rz for its surface of not more than 2 μm.
An image-forming method is disclosed in Japanese Patent Application Laid-open No. 2009-192901 that uses an intermediate transfer belt equipped with a water-repellent and oil-repellent fluorine-based coating that provides a low attachability to the surface.
However, no disclosure is made in Japanese Patent Application Laid-open No. 2003-202785 with regard to the attachability of the toner itself. The image-forming method disclosed in Japanese Patent Application Laid-open No. 2003-202785 does exhibit an excellent primary transferability in the primary transfer step. However, the secondary transferability in the secondary transfer step has in some cases been unsatisfactory due to the strong attachability of the toner to the intermediate transfer member. In addition, the cleaning performance for the surface of the intermediate transfer member has also been prone to be unsatisfactory.
In the image-forming methods disclosed in Japanese Patent Application Laid-open Nos. 2006-84840 and 2009-192901, the attachability of the intermediate transfer member is not large enough in comparison to the attachability of the photosensitive member and in addition the toner-to-toner attachment force is small. As a consequence, a uniform toner layer cannot be maintained during primary transfer and the problem of “middle dropout”—which is a transfer defect in which only the middle of, for example, a fine line, does not transfer—has readily occurred.